Inclusive production of $\mathrm{D^{*\pm}}$ mesons in two-photon collisions was measured by the L3 experiment at LEP. The data were collected at a centre-of-mass energy $\sqrt{s} = 189$ GeV with an ...integrated luminosity of $176.4 \mathrm{pb^{-1}}$. Differential cross sections of the process $\mathrm{e^+e^- \rightarrow D^{*\pm} X}$ are determined as functions of the transverse momentum and pseudorapidity of the $\mathrm{D^{*\pm}}$ mesons in the kinematic region $1$ GeV $ p_{T}^{\mathrm{D^*}} 5 $ GeV and $\mathrm{|\eta^{D^*}|} 1.4$. The cross section integrated over this phase space domain is measured to be $132 \pm 22(stat.) \pm 26(syst.) $ pb. The differential cross sections are compared with next-to-leading order perturbative QCD calculations.
Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at sqrt(s) 192 GeV. The distributions of several event shape variables are compared to ...resummed O(alphaS^2) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies demonstrate the running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +- 0.0058, where the first uncertainty is experimental and the second is theoretical.
A novel geometry for a sampling calorimeter employing inorganic scintillators as an active medium is presented. To overcome the mechanical challenges of construction, an innovative light collection ...geometry has been pioneered, that minimises the complexity of construction. First test results are presented, demonstrating a successful signal extraction. The geometry consists of a sampling calorimeter with passive absorber layers interleaved with layers of an active medium made of inorganic scintillating crystals. Wavelength-shifting (WLS) fibres run along the four long, chamfered edges of the stack, transporting the light to photodetectors at the rear. To maximise the amount of scintillation light reaching the WLS fibres, the scintillator chamfers are depolished. It is shown herein that this concept is working for cerium fluoride (CeF\(_3\)) as a scintillator. Coupled to it, several different types of materials have been tested as WLS medium. In particular, materials that might be sufficiently resistant to the High-Luminosity Large Hadron Collider radiation environment, such as cerium-doped Lutetium-Yttrium Orthosilicate (LYSO) and cerium-doped quartz, are compared to conventional plastic WLS fibres. Finally, an outlook is presented on the possible optimisation of the different components, and the construction and commissioning of a full calorimeter cell prototype is presented.
The three different helicity states of W
± bosons, produced in the reaction
e
+
e
−→
W
+
W
−→
ℓνq
q
̄
are studied using leptonic and hadronic W decays at
s
=183
GeV and 189 GeV. The W polarisation is ...also measured as a function of the scattering angle between the W
− and the direction of the e
− beam. The analysis demonstrates that W bosons are produced with all three helicities, the longitudinal and the two transverse states. Combining the results from the two center-of-mass energies and with leptonic and hadronic W decays, the fraction of longitudinally polarised W
± bosons is measured to be 0.261 ± 0.051(stat.) ± 0.016(syst.) in agreement with the expectation from the Standard Model.
The process e+ e- -> n gamma with n =2 is studied at centre-of-mass energies ranging from \root(s)=192 to 208 GeV. The data sample corresponds to a total integrated luminosity of 427 1/pb. The total ...and differential cross sections are found to be in agreement with the QED expectations. Using all the data collected with the L3 detector above the Z pole, limits on deviations from QED, excited electrons, contact interactions, extra space dimensions and excited spin-3/2 leptons are set.
The reactions $e^+e^- \to e^+e^-\pi^0$ X and $e^+e^- \to e^+e^-K^0_S$ X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive ...differential cross sections are measured as a function of the particle transverse momentum pt and the pseudo-rapidity. For $p_t \le 1.5$ GeV, the $\pi^0$ and $K^0_s$ differential cross sections are described by an exponential, typical of soft hadronic processes. For $p_t \ge 1.5$ GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations. \end{document}
The $\eta \pi^+ \pi^-$ final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209~GeV with an integrated luminosity of 664.6~pb$^{-1}$. ...The f$_1$(1285) meson is observed and the $Q^2$ dependence of its production is compared to different form factor models. The $\gamma\gamma$-coupling parameter $\tilde\Gamma_{\gamma\gamma}$ is found to be $3.5 \pm 0.6\,(stat.) \pm 0.5\,(sys.)$~keV. The branching fraction $\Gamma\bigl({\rm f
We search for a Higgs particle with anomalous couplings in the e
+e
−→H
γ, e
+e
−→HZ and e
+e
−→He
+e
− processes with the L3 detector at LEP. We explore the mass range
70
GeV
<m
H
<170
GeV
using
176
...pb
−1
of integrated luminosity at a center-of-mass energy of
s
=189
GeV
. The Higgs decays
H→
b
b
̄
, H→
γγ and H→Z
γ are considered in the analysis. No evidence for anomalous Higgs production is found. This is interpreted in terms of limits on the anomalous couplings
d,
d
B
,
Δg
1
Z and
Δκ
γ
. Limits on the
Γ(H→
γγ) and
Γ(H→Z
γ) partial widths in the explored Higgs mass range are also obtained.
Four of the Michel parameters and the average tau-neutrino helicity have been measured by analysing tau decay spectra in 147 pb
−1of data collected by the L3 detector. The decays
τ
−→
e
−ν
τ
ν
̄
e
,
...τ
−→
μ
−ν
τ
ν
̄
μ
,
τ
−→
π
−ν
τ
,
τ
−→
ρ
−ν
τ
and their charge conjugates were considered. The results:
ρ=0.762±0.035,
η=0.27±0.14,
ξ=0.70±0.16,
ξδ=0.70±0.11 and
ξ
h
=−1.032±0.031 are consistent with a V−A structure for the weak charged current and lepton universality.
Optimization of the silicon sensors for the CMS tracker Albergo, S.; Angarano, M.; Azzi, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2001, Letnik:
466, Številka:
2
Journal Article
Recenzirano
The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. ...Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker.
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